A multi-rotor helicopter is comprised of several groups of propellers or rotors which are distributed in a certain arrangement manner. The propellers are secured to arms, and arms are connected with a fuselage. This layout has a large size, and arms generally need to be folded to reduce the size upon carrying.
At present, ordinary folding methods comprise two manners: folding in opposed directions or folding in the same direction, which will be described below respectively.
Folding in opposed directions may comprise two manners: non-overlapping folding in opposed directions and overlapping folding in opposed directions, which will be described below respectively.
Non-overlapping folding in opposed directions: FIG. 1A is a top view of an unmanned helicopter employing arms which are non-overlappablely foldable in opposed directions when the arms are in a deployed state in the prior art. The figure does not show corresponding rotors installed at locations of motors 81, 82, 83, 84. As shown in FIG. 1A, when a sum of lengths of an arm 21 and an arm 22 is smaller than a length of the fuselage 1, non-overlapping folding in opposed directions can be performed. FIG. 1B is a top view of an unmanned helicopter employing arms which are non-overlappablely foldable in opposed directions when the arms are in a folded state in the prior art. As shown in FIG. 1B, the sum of lengths of the arm 21 and the arm 22 in non-overlapping folding is smaller than the length of the fuselage 1. A drawback of the arms which are non-overlappingly foldable in opposed directions is: the fuselage 1 is required to be longer, and relatively, the arms 21, 22, 23, 24 all are very short, so that the lengths of the arms are limited seriously. Therefore, if the lengths of arms are to be increased, the length or width of the fuselage needs to be increased at the same time so that the size after the folding becomes larger and the helicopter body becomes heavier.
Overlapping folding in opposed directions: FIG. 2A is a top view of an unmanned helicopter employing arms which are overlappablely foldable in opposed directions when the arms are in a deployed state in the prior art. The figure does not show corresponding rotors installed at locations of motors 81, 82, 83, 84. FIG. 2B is a top view of an unmanned helicopter employing arms which are overlappablely foldable in opposed directions when the arms are in a folded state in the prior art. As shown in FIG. 2A, a first rotation axis 31 and a second rotation axis 32 are disposed asymmetrically so that the arm 21 and arm 22 may partially overlap in the length direction of the fuselage 1. A drawback of the arms which are overlappingly foldable in opposed directions is: folding in opposed directions employs parallel axes, namely, rotation axes of a group of arms to be folded in opposed directions are parallel to each other, which causes an inter-axis distance between folding axes of the arms to be larger than the lengths of arms.
Folding in the same direction may comprise two manners: folding horizontally in the same direction and folding vertically in the same direction, which will be introduced respectively.
Folding horizontally in the same direction: FIG. 3A is a top view of an unmanned helicopter employing arms which are foldable in the same direction when the arms are in a deployed state in the prior art. The figure does not show corresponding rotors installed at locations of motors 81, 82, 83, 84. When arms are folded horizontally in the same direction, FIG. 3B is a top view of an unmanned helicopter employing arms which are foldable in the same direction when the arms are folded horizontally in the same direction in the prior art, wherein the arms 21, 22, 23 and 24 are all folded in the same horizontal direction towards one side of the fuselage 1. A drawback of the arms which are horizontally foldable in opposed directions is: the overall length in the folded state is larger than the length of a single arm plus the length of the fuselage.
Folding vertically in the same direction: FIG. 3A is a top view of an unmanned helicopter employing arms which are foldable in the same direction when the arms are in a deployed state in the prior art. The figure does not show corresponding rotors installed at locations of motors 81, 82, 83, 84. When arms are folded vertically in the same direction, FIG. 3C is a top view of an unmanned helicopter employing arms which are foldable in the same direction when the arms are folded vertically in the same direction in the prior art, wherein the arms 21, 22, 23 and 24 are all folded in the same direction and downwardly perpendicular to a plane where the fuselage 1 lies. A drawback of the arms which are vertically foldable in the same direction is: although the height in the folded state is only larger than the length of a single arm, an empty space formed by the fuselage area and the arm length is left in the middle, and the size in the folded state cannot be effectively reduced.